When Rosemary Squire came to see her son’s student productions at the Oxford Playhouse, she probably wasn’t immediately thinking that one day she would be boss of the New Theatre round the corner.

But that’s what has happened: Rosemary is joint chief executive of Ambassador Theatre Group, which has taken over the New Theatre from American-owned Live Nation, along with 16 other venues up and down the country.

The ATG story began when Rosemary met her future husband and co-chief executive, Howard Panter. He was producing a West End show, she was working in the box office.

“It was a fabulous thing. It was the first show where he had his name above the title, and was called And a Nightingale Sang. But sadly, try hard though he did, he just couldn’t sell enough tickets. He would come into the box office on a Saturday night, to know what the week’s takings were, and we would all be despairing. He would cheer us all up with very large gin and tonics: he would rally the troops, despite the fact that it was clearly a sinking ship.”

Beginning with just two theatres, the £90m (“Gulp” interjects Rosemary) acquisition of the Live Nation circuit means that ATG has now become the biggest theatre operator in Britain.

There will be three large ATG theatres in the region: the New Theatre, Milton Keynes Theatre, and the brand new Waterside, Aylesbury, due to open on October 12.

Will they all put on the same shows, I asked Rosemary, even though they’re only about 30 miles apart from each other?

“It’s not dissimilar to Woking, Wimbledon, and Richmond, where we have a triangle of theatres, all close to each other. But you do have to be careful, you have to work collaboratively between the venues involved.

“I think it’s very possible that the three theatres will play the same shows, but clearly not back to back.

“You’d need to stagger it, and have a decent gap in between. I think the potential for all three venues is very exciting.”

Existing ATG theatres like Milton Keynes tend to run shows for at least a week, whereas groups, bands, comics, even ballet companies often whizz through the New Theatre, staying for one night only. Will this change?

“I see evolution rather than revolution, hopefully keeping the very strong elements of each company. Live Nation have much better contacts than we do in the one-night gig world.

“So I’m hoping we will improve, and add, one nighters to our existing venues, and vice versa.”

Oxford’s New Theatre is not exactly the most comfortable place on earth to see a show, with its pins and needles-inducing lack of legroom, and cramped foyers. Are improvements planned?

“Live Nation have spent money, although perhaps not always in ways perceived by customers. They’ve just spent £50,000 improving disabled access.

“But with the restoration levy now added to ticket prices, we are able to spend more money on buildings. We have rolling budgets for improvements at all our venues, and we will also be talking to Oxford City Council about how we can upgrade the New Theatre — they own the venue, we have a lease on it.”

Also inherited from Live Nation are the OFS Studio in George Steeet, and offices in Cowley, originally the HQ of Live Nation’s predecessor Apollo Leisure, founded in Oxford by Paul Gregg.

“The OFS is not core to the portfolio, I have to say,” Rosemary told me. “But I’m looking forward to reopening discussions with the council. No firm decisions have been made.”

As for the Cowley offices, she added: “We want to sit back and gather our breath for a few months, and see what would be best.”

The massive growth of their ATG baby must surely mean that Rosemary Squire and husband Howard are living, eating, and sleeping theatre?

“It’s pretty hard not to, although our kids don’t like it. There are pluses and minuses. We started this meeting late because Howard wanted to talk about a key programming decision.

“We can have a five-minute conversation, which might take a two-hour meeting with another colleague. You don’t have to beat about the bush. The key thing is that we trust each other.

“The downside is that you’re never shot of it, and it colours your whole life.

“You have to pace yourself: even though, much as I hate it, I do go to the gym, our game is a lot of evenings, and I genuinely can’t do more than three evenings a week working.”